Small Modular Reactors (LWR designs)

I. Appropriate Source Term, Dose Calculations, and Siting for SMRs

Applicability: SMRs and non-LWRs

In the December 29, 2011, memorandum to the Commission, the staff stated it would remain engaged with SMR stakeholders regarding applications of mechanistic source term (MST) methods, review of pre-application white papers and topical reports it receives from potential SMR applicants concerning source term issues that discuss design-specific proposals to address MST, and considerations of research and development in this area. If necessary, the staff would propose revised review guidance or regulations, or propose new guidance to support reviews of SMRs.

In Commission Memoranda dated May 30, 2013, and June 20, 2014, the staff provided updates on interactions with U.S. Department of Energy (DOE) and nuclear industry organizations regarding MST. On February 7, 2016, the staff provided the Commission SECY 16-0012, which addressed this item. The paper concluded that (1) SMR and non-light water reactor (non-LWR) applicants can employ modern analysis tools to demonstrate quantitatively the safety features of those designs, and (2) MST analysis methods can also be used by applicants to demonstrate the ability of the enhanced safety features of plant designs to mitigate accident releases, allow future COL applicants to consider reduced distances to Exclusion Area Boundaries and Low Population Zones and potentially increase proximity to population centers.

Disposition: The staff continues to engage with interested stakeholders on this issue. The staff developed a draft white paper summarizing the assessment of current siting regulations, guidance, and Commission policy and discussed it in a public meeting on December 14, 2017. During a May 3, 2018, public meeting, NEI provided feedback on this topic on behalf of the nuclear industry. The NEI stated their position that Regulatory Guide (RG) 4.7, "General Site Suitability Criteria for Nuclear Power Stations," should be updated to scale the population density guidance based on the smaller source term and lower probability of release anticipated for SMRs and advanced reactors. In June 2019, Oak Ridge National Laboratory completed a technical report ORNL/TM-2019/1197, "Advanced Reactor Siting Policy Considerations," identifying potential alternative siting criteria for SMRs and non-LWRs recognizing the possible reduced offsite releases for advanced reactor designs. The report provided insights to inform the staff's plans to develop additional regulatory guidance for SMR and non-LWR siting. On June 13, 2019, the staff released a second draft white paper, "Population-Related Siting Considerations for Advanced Reactors," to facilitate stakeholder discussions at a public meeting that was held on June 27, 2019. The staff addressed stakeholder feedback and issued a draft SECY paper on July 19, 2019 to support meetings with the ACRS subcommittee on August 23, 2019, and with the ACRS Full Committee 0n September 4, 2019. The staff provided SECY-20-0045, "Population Related Siting Considerations for Advanced Reactors," to the Commission on May 8, 2020. In SECY-20-0045, the staff provided options and a recommendation to the Commission on possible changes to guidance documents to address population-related siting considerations for advanced reactors. The staff's recommendation is to pursue a revision to the population-related siting guidance used to implement Commission policy to provide technology-inclusive, risk-informed, and performance-based criteria to assess certain population-related issues in siting advanced reactors.

SECY-20-0045 (05/08/20)

Draft SECY paper
(07/19/2019)

Staff White Paper (06/13/2019)

Staff Draft White Paper (11/29/17)

SECY-16-0012 (02/07/16)

Commission Memo (06/20/14)

Commission Memo (05/30/13)

Commission Memo (12/29/11)

II. Offsite Emergency Planning (EP) Requirements for SMRs and other new technology

Applicability: SMRs and non-LWRs

In SECY-11-0152, the staff identified a possible approach for a scalable emergency planning zone for SMRs. The NRO staff is working with NSIR and NRR on an internal working group to review these issues further. As part of the approach, the staff would liaise with other stakeholders (Department of Homeland Security/Federal Emergency Management Agency, the Environmental Protection Agency, Department of State, Department of Commerce, NEI, American Nuclear Society, and the public), consider NEI position papers on this topic and develop recommendations.

In a May 30, 2013, Commission memorandum, the staff provided updates on its EP activities. The staff stated that it would not propose new policy or revise guidance for specific changes to EP requirements absent specific proposals from industry stakeholders.

On December 23, 2013, NEI submitted a white paper on this topic. The staff conducted a public meeting to discuss the white paper on April 8, 2014, issued follow-up questions to NEI on June 11, 2014, and received NEI responses in November 2014. On May 29, 2015, the staff issued SECY-15-0077 regarding EP for SMRs and non-LWRs. On August 4, 2015, the Commission approved the staff's recommendation to initiate a rulemaking. The staff developed SECY-16-0069, which discussed the rulemaking plan and schedule. On June 22, 2016, the Commission approved the staff's plan and schedule for the rulemaking.

Disposition: The rulemaking will address EP issues for future SMRs and other new technologies, including non-LWRs and medical radioisotope facilities. The Commission directed the staff to utilize exemptions in the interim (e.g., for the TVA ESP) until completion of the EP rulemaking. The draft regulatory basis was published for public comment in the Federal Register on April 13, 2017. A public meeting was held May 10, 2017, to discuss the draft regulatory basis. The public comment period closed on June 27, 2017. After considering the public comments, the staff issued the final regulatory basis on October 16, 2017. The staff discussed this rulemaking during a June 14, 2018, stakeholder meeting. The staff released the draft proposed rule language on August 1, 2018 to support ACRS briefings on August 22 and October 4, 2018. The proposed rule was provided to the Commission for its consideration in SECY-18-0103 on October 12, 2018. On December 17, 2019, in SRM-SECY-18-0103, the Commission approved publication of the proposed rule. On May 12, 2020, the staff published the proposed rule in the Federal Register (85 FR 28436) for public comment. The schedule for the final rule is available on the NRC’s rulemaking website.

Proposed Rule (85 FR 28436 05/12/20)

SRM-SECY-18-0103

SECY-18-0103 (10/12/18)

Final Regulatory Basis (10/16/17)

SRM-SECY-16-0069 (06/22/16)

SECY-16-0069 (05/31/16)

SRM-SECY-15-0077 (08/04/15)

SECY-15-0077 (05/29/15)

NEI Response to NRC Questions on White Paper (11/19/14)

NRC Letter to NEI (R. Bell) (06/11/14)

NEI White Paper (12/23/13)

Commission Memo (05/30/13)

SECY-11-0152 (10/28/11)

III. Insurance and Liability for SMRs

Applicability: SMRs and non-LWRs

In SECY-11-0178, the staff identified a potential inequity between the insurance requirements for facilities with power reactors that produce electrical power equal or greater than 100 MWe per unit and multi-module facilities with SMR designs that individually produce less than 100 MWe, but, in combination, produce more than 100 MWe. Specifically, the staff raised the question of whether, under the current Price-Anderson Act and associated regulatory language, insurance and indemnity coverage would be sufficient to pay all public claims in the case of an insurable event at a multi-module facility where an individual module is sized at less than 100 MWe.

Since completing that paper, the staff prepared a comparative analysis of different SMR designs to further explore the potential inequity. The staff is also evaluating the differences in potential consequences for postulated accidents for non-LWR designs in relation to insurance and liability requirements. The staff is using these analyses, and other inputs, to identify whether to recommend any changes to the Price-Anderson Act for SMRs and non LWRs.

Disposition: In accordance with the latest version of the Price-Anderson Act, the NRC will prepare a report to Congress, and an associated SECY paper, for the Commission's consideration, recommending the need for continuation or modification of the provisions of the Price-Anderson Act by December 31, 2021. This report and SECY paper will address any changes that the staff recommends for non-LWRs and SMRs.

The staff engaged stakeholders on this topic during a November 2, 2017, public meeting and the staff will continue to keep stakeholders informed as the report to Congress is prepared.

SECY-11-0178 (12/22/11)

IV. Security and Safeguards Requirements for SMRs

Applicability: SMRs and non-LWRs

On December 14, 2016, NEI submitted a white paper on a "Proposed Consequence-Based Physical Security Framework for Small Modular Reactors and Other New Technologies." This paper "... proposes an approach to security that considers the enhanced safety and security incorporated into these designs and provides a more effective and efficient means to protect the public health and safety." In the transmittal letter, NEI requests that "... the NRC establish regulatory positions on this approach and the associated policy and technical issues."

Disposition: The NRC met with NEI on May 3, 2017, to discuss the review of their submittal. The NRC provided feedback on NEI's white paper in July 2017, and met with NEI again on October 12, 2017. The staff prepared a draft white paper to facilitate stakeholder interactions. The staff discussed this white paper with NEI and other stakeholders on December 13, 2017. The staff considered stakeholder input and prepared SECY-18-0076, "Options for Physical Security For Light-Water Small Modular Reactors And Non-Light-Water Reactors," which was sent to the Commission on August 1, 2018. On November 19, 2018, the Commission directed the staff to initiate a limited-scope revision to regulations and guidance related to physical security for advanced reactors and approved, subject to edits, a related rulemaking plan. At a December 13, 2018, Advanced Reactor Stakeholder meeting, participants discussed the scope of potential changes to physical security requirements. The staff preparing a regulatory basis which was published in the Federal Register on July 16, 2019, for public comment. The staff discussed the regulatory basis with stakeholders during an August 8, 2019 public meeting and will consider comments on the regulatory basis as it prepares the draft proposed rule. The staff discussed the proposed rulemaking approach during a public meeting on December 12, 2019. The staff also discussed preliminary proposed rule text and the NRC staff's disposition of public comments screened out of this rulemaking during an April 22, 2020 public meeting.

Regulatory Basis (07/16/2019)

SECY-18-0076 (08/01/18)

Staff Draft White Paper (11/29/17)

NEI White Paper (12/14/16)

SECY-11-0184 (12/29/11)

Functional Containment Performance

Applicability: Non-LWRs

In SECY-93-0092, "Issues Pertaining to the Advanced Reactor (PRISM, MHGTR, and PIUS) and Candu 3 Designs and their Relationship to Current Regulatory Requirements," the staff proposed to evaluate the acceptability of proposed designs using a standard based upon containment functional performance rather than to rely exclusively on prescriptive containment design criteria. The staff also informed the Commission that it intended to approach this by comparing containment performance with the accident evaluation criteria. In SRM-SECY-93-0092, the Commission approved the staff's recommendation.

Subsequently, in SECY-03-0047, the staff recommended that the Commission approve the use of functional performance requirements to establish the acceptability of a containment or confinement structure (i.e., a non-pressure retaining building may be acceptable provided the performance requirements can be met) and the staff proposed that functional performance requirements be developed. In SRM-SECY-03-0047, the Commission disapproved the staff's recommendation stating that there was insufficient information at the time for the Commission to prejudge the best options and make a decision on the viability of a confinement building. The Commission directed the staff to develop performance requirements and criteria working closely with industry experts (e.g., designers, EPRI, etc.) and other stakeholders regarding options in this area, taking into account such features as core, fuel, and cooling systems design. The Commission also directed the staff to pursue the development of functional performance standards and then submit options and recommendations to the Commission.

In SECY-05-0006, the staff discussed many of the concepts developed in previous communications between the staff and Commission on the topic of functional containment performance and, as directed in SRM-SECY-03-0047, outlined the attributes for a functional containment. The topic of functional containment was also addressed as part of the next-generation nuclear plant (NGNP) project in the context of high-temperature gas-cooled reactors. In light of the broad range of non-light water designs under consideration, the staff engaged the Commission to confirm whether the existing Commission direction in SRM-SECY-93-0092 should be applied more broadly to additional advanced reactor designs and to propose a risk-informed, performance-based approach to establishing performance criteria for structures, systems, and components and corresponding programs to limit the release of radioactive materials from advanced reactors.

Disposition: The staff has engaged stakeholders on this topic at several public meetings. The staff prepared a draft white paper on functional containment performance to facilitate stakeholder interactions. The staff discussed this white paper with stakeholders on December 14, 2017, and February 1, 2018, and with the ACRS on February 22, 2018, and April 5, 2018. The ACRS provided a letter on May 10, 2018. The staff considered ACRS and stakeholder feedback and prepared SECY-18-0096, "Functional Containment Performance Criteria for Non-Light-Water-Reactors," that was provided to the Commission on September 28, 2018. In SECY-18-0096, the staff recommended Commission approval of a proposed methodology for establishing functional containment performance criteria for non-light-water-reactors in a manner that is technology inclusive, risk informed, and performance based. In SRM-SECY-18-0096, the Commission approved the staff’s proposed methodology for establishing functional containment performance criteria for non-LWRs.  The Commission also requested that the staff continue to keep them informed as it develops the licensing framework for non-LWRs and notify the Commission if future policy issues arise as this work progresses.  The staff is incorporating the methodology for functional containment performance criteria in ongoing activities, such as the preparation of DG-1353, future revisions of RG 1.232, and interactions with specific designers.

SECY-18-0096 (09/28/18)

Staff Draft White Paper (11/27/17)

SECY-05-0006 (01/07/05)

SMR-SECY-03-0047 (06/26/03)

SECY-03-0047 (03/28/03)

SRM-SECY-93-092 (07/30/93)

SECY-93-092 (04/08/93)

License for Prototype Reactors

Applicability: Principally non-LWRs

No policy issues or rulemaking needs were identified by staff in SECY-11-0112, which informed the Commission of the results of the staff's assessment of several potential licensing issues and key technical issues for SMRs that were identified in SECY-10-0034. The staff developed and implemented issue resolution plans for each issue discussed in SECY-10-0034. While there is no Commission policy issue to be addressed, misunderstanding of the term "prototype" by stakeholders contributes to uncertainty about what constitutes a prototype and the licensing criteria for a prototype.

Disposition: The staff developed guidance regarding implementation of the prototype language in 10 CFR 50.43(e). On June 16, 2017, the NRC issued a preliminary draft document, "Nuclear Power Reactor Testing Needs and Prototype Plants for Advanced Reactor Designs." This document described the relevant regulations governing the testing requirements for advanced reactors, described the process for determining testing needs to meet the NRC's regulatory requirements, clarified when a prototype plant might be needed and how it might differ from the proposed standard plant design, and described licensing strategies and options that include the use of a prototype plant to meet the NRC's testing requirements. The document was discussed during periodic public meetings on advanced reactor topics. After consideration of stakeholder feedback, the staff issued the final guidance in December 2017 as part of its Regulatory Review Roadmap.

Regulatory Review Roadmap (12/2017)

SECY-11-0112 (08/12/11)

SECY-10-0034 (03/28/10)

License Structure for Multi-Module Facilities

Applicability: SMRs and multi-module non-LWRs

In SECY-11-0079, the staff reviewed three potential licensing structure alternatives for multi module facilities and determined that Alternative 3 - licensing each module individually was preferred. Additional analysis will be performed by the staff to determine how best to address specific details associated with this alternative, including: licensing of common SSCs associated with the modules; the license duration for individual modules; and decommissioning considerations.

In the SECY, the staff committed to further develop specific aspects of Alternative 3 and will submit a specific proposal to the Commission for its consideration and approval.

Disposition: The staff evaluated this issue and determined its preferred path forward in the 2011 SECY. This policy issue is now closed.

SECY-11-0079 (06/12/11)

SMR Variable Annual Fees

Applicability: SMRs only

In a February 7, 2011 memorandum from the Chief Financial Officer (CFO) to the Commission, the staff developed an approach to address the equitable assessment of annual fees to small modular reactors (SMRs). The memo stated that Commission approval for the approach will be requested during development of the proposed rule.

In July 2014, the Office of the Chief Financial Officer established a follow-up working group to draft a SECY paper, proposed rule, and final rule for the SMR variable annual fee structure.

SECY-15-0044 for proposed SMR variable annual fees was issued on 03/27/2015 and the SRM was issued on 05/15/2015. In the SRM, the Commission approved the staff's recommendation to initiate rulemaking. The proposed rule was issued for public comment on 11/4/2015. The final rule became effective on June 23, 2016.

Disposition: The NRC published the proposed rule, "Variable Annual Fee Structure for Small Modular Reactors," in the Federal Register for public comment on Nov. 4, 2015, and held a public meeting on Nov. 16, 2015. The final rule (with administrative corrections) became effective July 15, 2016. The rulemaking dispositions this issue for SMRs.

In the future, the OCFO staff will likely reconsider the specific values used in determining the variable annual fees based on experience with the first SMRs, and periodically into the future, just as is done with the existing reactor fleet.

This policy issue is now resolved for SMRs. The staff will review this policy topic at the appropriate time in the future for applicability to small non-LWRs.

Final Rule Variable Annual Fee Structure for Power Reactors (05/16/16)

Draft Regulatory Analysis (10/06/15)

SRM-SECY-15-0044 (5/15/15)

SECY-15-0044 (03/27/15)

Memo to Commission from CFO (02/07/11)

Manufacturing License Requirements for Future Reactors

Applicability: SMRs and non-LWRs

Staff has studied the issue and discussed it with the SMR community in public meetings. No current technical issue or policy issue was identified for resolution and no interest in obtaining a manufacturing license from near-term SMR applicants was expressed.

Disposition: This issue is closed and no further staff action is needed at this time.

Commission Memo (03/27/13)

Use of Probabilistic Risk Assessment in the Licensing Process for SMRs

Applicability: SMRs and non-LWRs

The staff has engaged with public stakeholders and has developed expanded guidance for this topic by providing criteria to ensure appropriate treatment of important insights related to multi-module design and operation. The expanded guidance is consistent with current Commission policy and objectives for the use of probabilistic risk assessment (PRA) in the design, certification, and licensing of advanced light-water reactors.

Additionally, the staff plans to implement a risk-informed review methodology for SMRs, such as the NuScale design, that uses a four-category structures, systems, and components (SSCs) review approach: (1) safety-related and risk significant; (2) safety-related and non-risk significant; (3) non-safety-related and risk significant; and (4) non-safety-related and non-risk significant.

Disposition: This additional PRA guidance has been incorporated into SRP 19.0, Revision 3, "Probabilistic Risk Assessment and Severe Accident Evaluation for New Reactors," which was issued in the Federal Register on February 09, 2016. The effective date is March 10, 2016. This issue is considered closed.

SECY-11-0079 (06/12/11)

Key Component and System Design Issues for SMRs

Applicability: SMRs and non-LWRs

Policy impacts on key components and system designs are design-specific and will be evaluated for individual applications. Examples of potential design features that could have policy impacts have been identified for the NuScale design. These include the use of a common pool as the ultimate heat sink for all plant modules and spent fuel, and the proposed electrical system design without the need for offsite power sources.

Disposition: This issue is considered closed and no further staff action is needed at this time because it has been determined to be design-specific.

No further general references have been developed by the staff for this item

Appropriate Requirements for Operator Staffing for Small or Multi-Module Facilities

Applicability: SMRs and non-LWRs

In SECY-11-0098, staff concluded that evaluating applicant operator staffing exemption requests is the best short-term response for this issue. The SECY discussed performing updates of NUREG-0800, NUREG-0711, and NUREG-1791 for guidance of the short-term evaluations. Staff now concludes that the existing version of SRP Chapter 18 and Revision 3 to NUREG 0711 (published November 2012) comprise adequate guidance for performing the exemption request evaluations.

More recently the staff communicated with NuScale, LLC, during the NuScale preapplication review. By letter dated January 16, 2016, the staff provided clarification of the process NuScale could use to address this issue in their design certification application.

On April 8, 2016, NuScale, LLC, responded to the staff's January 16, 2016, letter, and described how NuScale planned address 10 CFR 50.54(m) requirements.

Disposition: This issue is considered closed and no further staff action is needed at this time.

Letter (04/08/16)

Letter (01/14/16)

NUREG-0711, Rev. 3 (11/2012)

SECY-11-0098 (07/22/11)

Operational Programs for Small or Multi-Module Facilities

Applicability: SMRs and non-LWRs

The potentially unique design features and operating characteristics of SMRs may require new or revised operational programs to maintain appropriate periodic surveillance and operational oversight. Examples of these features could include helical coil steam generators, allowances for extended refueling cycles, and the use of robotic machines for component disassembly and reassembly.

In SECY-11-0112, the staff determined that these design-specific features and programs would be adequately reviewed during technical application reviews with no additional guidance, rulemaking, or policy changes needed.

Disposition: This issue is considered closed and no further staff action is needed at this time.

SECY-11-0112 (08/12/11)

Installation of Reactor Modules During Operation of Multi-Module Facilities

Applicability: SMRs and multi-module non-LWRs

The proximity of individual modules within common structures or facilities for multi-module SMRs could introduce technical concerns such as heavy load handling, potential refueling operation impacts with operating modules, and installation of new modules in an operating plant environment. As discussed in SECY-11-0112, the staff determined that these technical matters will be identified by the applicant and assessed by the staff during design certification application reviews. Therefore this issue can be addressed with current guidance, and no rulemaking or policy changes are needed.

Disposition: This issue is considered closed and no further staff action is needed at this time.

SECY-11-0112 (08/12/11)

Industrial Facilities Using Nuclear-Generated Process Heat

Applicability: SMRs and non-LWRs

The co-location of a nuclear power plant (NPP) and an industrial facility using process heat from the NPP introduces a number of technical and regulatory jurisdiction issues into the NRC's licensing process. As discussed in SECY-11-0112, with the exception of liability and insurance considerations, these issues are expected to be primarily technical in nature and will not require policy changes. Issues identified during technical reviews are expected to be addressed using current guidance; no rulemaking or policy changes should be needed. Examples of the potential technical issues include the effects of the reactor on the adjacent industrial facility products and staff. Other related issues, such as plant siting, would be reviewed on a case by case basis in accordance with existing guidance and requirements.

This approach may be re-assessed in the future depending on the technical details of a specific application However, since there are so many potential configurations of NPP designs and industrial facilities, the staff cannot make further judgements at this time.

Disposition: This issue is considered closed and no further staff action is needed at this time.

SECY-11-0112 (08/12/11)

Decommissioning Funding Assurance for SMRs

Applicability: SMRs and non-LWRs

SECY-11-0181 informed the Commission of the staff's plans to ensure that SMR licensees provide reasonable assurance that funding will be available for decommissioning. The near-term approach will be to consider allowing SMR applicants to deviate from existing regulations through exemption requests with supporting analysis. Applicants may submit a site-specific estimate of decommissioning costs with a supporting analysis and adequate justification for an exemption to the minimum funding requirements for large LWRs shown in 10CFR50.75. The estimate to be provided will account for individual modules and common elements and structures as applicable.

Disposition: This issue is considered closed and no further staff action is needed at this time.

SECY-11-0181 (12/22/11)

Implementation of Defense-In-Depth (DiD) Philosophy for Advanced Reactors

Applicability: SMRs and non-LWRs

As described in SECY-10-0034, the issue of DiD was focused on non-light-water SMRs. In SECY-09-0056, the staff proposed to defer development of a DiD policy statement pending gaining additional experience and related insights from Next-Generation Nuclear Plant or other non-LWR reviews.

More broadly, the concepts and goals of DiD as applied generally to a technology neutral regulatory framework was discussed in Enclosure 3 of the staff's recommendations for disposition of NRC Fukushima Near Term Task Force Recommendation 1 (SECY 13 0132).

In SRM-SECY-13-0132, the Commission disapproved SECY-13-0132 Improvement Activity 2, "Establish Commission Expectations for Defense-in-Depth" and directed the staff to re-evaluate the topic as appropriate in the context of the Commission direction on a long-term Risk Management Regulatory Framework (RMRF).

Disposition: In SRM-SECY-15-0168 on RMRF, the Commission approved the staff's recommendation that the NRC not develop a definition of and criteria for determining adequacy of defense in depth and directed the staff to expeditiously complete the revision to Regulatory Guide 1.174 on defense in depth, in order to improve the clarity of the guidance.

NRO staff will implement the Commission decision with respect to DiD. Further, DiD is considered to be part of a risk-informed review framework, such as the one planned for use with the NuScale SMR design.

SECY-15-0168 (12/18/15)

SRM-SECY-13-0132 (05/19/14)

SECY-13-0132 (12/11/13)

SECY-13-0132, Enclosure 3: Defense-In-Depth Observations and Detailed History (12/11/13)

Regulatory Guide 1.174, Rev. 2 (05/31/11)

SECY-09-0056 (04/07/09)

Aircraft Impact Assessments for SMRs

Applicability: SMRs and non-LWRs

10 CFR 50.150 requires design and license applicants for new nuclear power reactors to perform a design specific assessment of the effects on a facility of the impact of a large commercial aircraft. Using realistic analyses, the applicant shall identify and incorporate into the design those design features and functional capabilities to show that, with reduced operator actions: (i) The reactor core remains cooled, or the containment remains intact; and (ii) spent fuel cooling or spent fuel pool integrity is maintained.

In SECY-11-0112, the staff determined that this technical issue did not involve a policy question, and that the issue could be addressed with current guidance during the design certification and licensing reviews. No rulemaking or policy changes are needed.

Disposition: For LWR designs, this issue is considered closed and no further staff action is needed at this time.

As described in the referenced SECY, for non LWRs, additional guidance may be beneficial to address potential unique features of the advanced designs, such as the majority of structures being located below grade. The staff will keep the Commission informed and will develop the guidance at a time consistent with the maturity of the design (industry), if necessary.

SECY-11-0112 (08/12/11)